This invention relates to fuel cell stacks and more particularly to the plate structure used at the ends of such stacks.
It is conventional in fuel cell design to arrange individual fuel cells one on top of the other and to compress this stack of cells between two terminal or end plates. In addition to the compressive forces provided to the stack by the end plates, these plates also provide the stack with access to the external circuit containing the load as well as provide the spacing needed to seal reactant gases from the atmosphere.
Previously, particularly in molten carbonate fuel cell stacks, the cells immediately adjacent the end plates experience a performance loss, associated with an increase in cell internal resistance. Poor compliance of the components of these end cells is believed to be the primary reason for this higher internal resistance and attendant lower performance. This poor compliance, in turn, is believed to be attributable to the rigid nature of the stack end plates which are far less tolerant to cell component thickness variations than are the sheet-metal bipolar plates used between intermediate cells in the stack.
It is therefore a primary object of the present invention to provide plate structure for the end plates of a fuel cell stack which does not suffer from the above disadvantages.
It is a further object of the present invention to provide plate structure for the end plates of a fuel cell stack which inhibits increases in the internal resistance exhibited by the adjacent end cells of the stack.
It is another object of the present invention to provide plate structure for the end plates of a fuel cell stack which results in better compliance of the components of the end cells of the stack.
It is yet a further object of the present invention to provide plate structure for the end plates of a fuel cell stack which exhibits greater resiliency than heretofore constructed plates.